This invention relates to air filters, and more particularly, to an in-line air filter for use with dry bulk tank trailers.
Over-the-road trailers are used to haul dry, bulk commodities. Typically, the truck to which such a trailer is hitched has a vacuum pump. An air line is attached to an outlet of the pump and is routed to the outlet section of various compartments (hoppers) within the trailer in which commodities are stored. These outlet sections usually include a manifold to which the air line is attached. The vacuum pump is used to generate an air flow by which vacuum pressure is produced at the outlets to create a suction through which force the commodity stored therein is drawn from the hoppers, entrained in the airstream, and directed to a storage location. It is possible for dirt and dust particles, and pieces of rust or other deleterious materials which have flaked off the internal parts of the pump, to be entrained in the airstream. These particles, if allowed to remain in the airstream, can contaminate the lading and either greatly reduce its value or render it worthless. To prevent this, filter assemblies are used in the air line to remove the dust, dirt and rust particles. These assemblies are installed in-line between the pump and the trailer.
Heretofore, the filters used have been paper element type filters. These exhibit a number or problems. First, they tend to disintegrate at air temperatures of between 300-350 degrees F. which can readily occur on a 100 degree F. ambient temperature day. Thus, the filter may fail completely, or not work as effectively as it should. In either event, the contamination problem noted above can occur. Secondly, the filters are not made to filter out smaller particles (40 microns or less), and therefore there is a great likelihood that minute dust, dirt, and rust particles will contaminate the lading. Third, the filters are not effective in reducing back pressure on the pump. Fourth, the filters are physically large in size and so are not easy to store. Lastly, the paper filters need frequent replacement which is time consuming and therefore costly both as to the filters required and the down-time needed to replace them.